1. Field of the Invention
The present invention relates to electro-optical systems. More specifically, the present invention relates to autofocus apparatus for electro-optical systems.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
Electro-optical lens systems are currently used in many missiles to provide an image which is converted into an electrical signal for display, guidance and/or processing. For missile and other guided vehicle applications, a highly accurate autofocus system is required to automatically focus the lens in response to a control signal. For these applications, the required accuracy is on the order of 100 times the accuracy of autofocus systems for a typical Browning camera. Hence, the tolerances and clearances of conventional autofocus systems for missiles are critical.
The conventional autofocus system for a missile is characterized by the movement of the lens within a threaded shaft. Unfortunately, the threaded shaft tends to adversely affect the optical train of the system. That is, the tolerances of such systems are such that the slight tilting of the lens, resulting from the use of the threaded drive, are sufficient to move the image off the center of the lens.
Further, it is often difficult to move the lens in a smooth manner on the threaded shaft without substantial lubrication. Yet, the use of a lubricant is problematic in that it often dries or dissipates. In addition, lubrication must be used with care to avoid contamination of the lens.
Conventional autofocus systems also tend to be electrically and mechanically unstable, suffer low yields in fabrication, exhibit latent failure modes and tend to be unreliable.
Thus, there is a need in the art to improve the performance and manufacturability of autofocus systems used in missile guidance and other demanding applications.